RESOURCE MANIPULATION THROUGH ARCHITECTURAL MODIFICATION OF THE HOST-PLANT BY A GALL-FORMING WEEVIL URODONTUS-SCHOLTZI LOUW (COLEOPTERA, ANTHRIBIDAE)

The manner in which a gall-inducing weevil, Urodontus scholtzi Louw, i nfluences the growth pattern of its host plant, Galenia africana (Aizo aceae), was studied in Namaqualand, South Africa. Galled stems increas ed by twice the diameter relative to paired ungalled stems in the firs t and second years and by more than three times in the third year afte r galling. Stems opposite or distal to the galled stem frequently died , reaching 54% mortality of opposite stems after one year and over 80% after three years. Although the weevils have a two-year life cycle, t he dominance of galled stems persists for at least four years and prob ably indefinitely Resources are manipulated by the weevil when first i nstar larvae cut partially through Vascular tissue, and by an unknown method of creating a strong sink for resources flowing up the stem. Su rvival in the gall was remarkably high at all sites, with 84-75% of ga lls containing adult weevils.